Add oats and sunflowers to a food processor and process until the texture of flour.
Add the cocoa powder, baking powder, pure stevia extract and salt.
Process until combined.
Pour in the wet ingredients along with the vanilla extract and liquid stevia and process until smooth.
On a parchment lined baking sheet or silpat, spoon 1 1/2 tablespoon mounds of batter totaling 18 mounds. (may need two baking sheets to allow 2-3 inches of spacing between mounds)
Bake 10-12 minutes and allow to cool completely before adding filling.
Once cooled, mix the filling ingredients in a stand mixer until whipped and fluffy.
Spread filling (about 1 tablespoon) onto one half and top with the second cookie.